Pharynx and deep neck spaces
Oral cavity, salivary glands, pharynx and the deep spaces of the neck
The mouth, salivary glands and pharynx are imaged by ultrasound, sialography, CT and MRI, and lesions are localised by which deep neck space they arise in. CPSP asks about tongue nerve supply and lymph drainage, the parotid and submandibular glands, the nasopharynx and the fascial spaces through which infection and tumour spread.
Tongue and palate
| Function | Anterior two-thirds | Posterior third |
|---|---|---|
| General sensation | Lingual nerve (V3) | Glossopharyngeal (IX) |
| Taste | Chorda tympani (VII) | Glossopharyngeal (IX) |
| Motor | Hypoglossal (XII); palatoglossus is the exception (vagus) | Hypoglossal (XII) |
- A lower motor neurone XII lesion: the tongue deviates towards the side of the lesion. Months later the denervated half is shrunken and bright on T1 from fatty replacement, and can make the normal side look like a mass.
- Genioglossus holds the tongue forward; loss of its tone under anaesthesia obstructs the airway, relieved by jaw thrust.
- Lymph drainage: tip to submental nodes; lateral anterior two-thirds to ipsilateral submandibular nodes; posterior third and midline lesions to deep cervical nodes of both sides.
- Palate: levator veli palatini (vagus) lifts the palate, and with a vagal lesion the uvula deviates away from the lesion. Tensor veli palatini (V3) is the main opener of the Eustachian tube, so cleft palate children get glue ear.
- Cleft lip is failure of the maxillary and medial nasal prominences to fuse; cleft of the secondary palate is failure of the lateral palatine shelves (fusing at about 7–10 weeks). Pierre Robin sequence starts with mandibular hypoplasia.
Salivary glands
| Feature | Parotid | Submandibular | Sublingual |
|---|---|---|---|
| Secretion | Serous | Mixed, mostly serous (serous demilunes) | Mostly mucous |
| Duct opening | Opposite upper second molar, through buccinator | Sublingual papilla beside the frenulum | Many small ducts on the sublingual fold |
| Secretomotor route | Inferior salivatory nucleus, IX, lesser petrosal, otic ganglion, auriculotemporal nerve | Superior salivatory nucleus, VII, chorda tympani, submandibular ganglion | As submandibular |
| Key relation | Facial nerve (most superficial), retromandibular vein, external carotid (deepest) | Wraps round the posterior border of mylohyoid; lingual nerve loops under the duct | Ranula arises here |
- The facial nerve is not seen on routine CT, so the retromandibular vein marks the plane between the superficial and deep lobes. Deep lobe tumours pass through the stylomandibular tunnel into the prestyloid parapharyngeal space as a dumbbell mass.
- Stones: about 80% are submandibular, because its saliva is more alkaline and mucous with more calcium, and its duct runs uphill. Many show on an occlusal film; ultrasound finds lucent ones.
- Plunging ranula: a thin-walled cyst from the sublingual gland passing round the back of mylohyoid into the submandibular space, with a tail in the sublingual space.
- The parotid is enclosed in a tight fascial capsule, so mumps is very painful. Frey syndrome after parotidectomy is misdirected parasympathetic fibres reaching sweat glands; the marginal mandibular nerve is at risk in submandibular surgery.
| Parotid lesion | Imaging clue |
|---|---|
| Pleomorphic adenoma | Well-defined lobulated mass, very bright on T2 |
| Warthin tumour | Tail of parotid, older male smoker, often bilateral; hot on pertechnetate (mitochondria-rich oncocytes) |
| Malignancy | Low T2 signal, ill-defined edge, facial palsy |
| Sjögren syndrome | Punctate sialectasis on sialography; watch for MALT lymphoma |
| HIV | Bilateral lymphoepithelial cysts with large adenoids and nodes |
| Sialadenosis | Bilateral uniform enlargement, no mass (alcohol, diabetes) |
Pharynx
- Nasopharynx: the adenoid (pharyngeal tonsil) lies on the posterosuperior wall and narrows the airway on a lateral soft-tissue film in children. The fossa of Rosenmüller (lateral recess behind the torus tubarius) is the commonest site of nasopharyngeal carcinoma, which blocks the Eustachian tube and causes a one-sided middle ear effusion in an adult. A Tornwaldt cyst is a midline, non-enhancing cyst of the posterior wall.
- Oropharynx: the palatine tonsil (non-keratinised stratified squamous epithelium with crypts) is supplied mainly by the tonsillar branch of the facial artery; IX lies in its bed, so tonsil pain is referred to the ear. Quinsy is pus between the tonsil capsule and superior constrictor. A cystic level II node with a small tonsil mass in a non-smoker suggests HPV-16 carcinoma.
- Hypopharynx: the valleculae (between tongue base and epiglottis) and piriform fossae hold residue on barium swallow when pharyngeal muscles or hyolaryngeal elevation are weak.
- The pterygomandibular raphe joins buccinator to superior constrictor; retromolar tumours spread along it.
Deep spaces of the suprahyoid neck
| Space | Contents | Typical lesion |
|---|---|---|
| Prestyloid parapharyngeal | Fat, minor salivary rests | Deep-lobe parotid tumour; displaced by masses around it |
| Carotid (poststyloid) | ICA, IJV, IX–XII, sympathetic chain | Paraganglioma, vagal schwannoma |
| Masticator | Ramus, masseter, pterygoids, temporalis, V3 | Odontogenic abscess with trismus |
| Retropharyngeal | Fat, lateral retropharyngeal nodes (in children) | Child abscess after upper respiratory infection |
| Danger space | Behind the retropharyngeal space, down to the posterior mediastinum | Mediastinitis |
| Prevertebral | Longus colli and capitis | Calcific tendinitis: calcification in front of C1–C2, effusion without rim enhancement |
| Buccal | Fat, parotid duct, accessory parotid | Cheek mass |
- A widened prevertebral soft-tissue shadow on a lateral neck film (more than about 7 mm at C2 in adults) suggests a retropharyngeal collection; in infants a film in expiration or flexion can falsely widen it.
- Branchial anomalies: a second cleft tract opens at the lower anterior border of sternocleidomastoid and runs between the internal and external carotid arteries to the tonsillar fossa; a first cleft anomaly lies in the parotid and runs towards the external ear canal.
Remember Facial nerve, vein, artery: superficial to deep in the parotid.
Exam trap The tongue deviates towards a lower motor neurone XII lesion, but the uvula deviates away from a vagal lesion.
Exam trap A cystic neck mass in an adult is a nodal metastasis until proven otherwise, not a branchial cyst.
Test yourself on this topic
5 of the 63 questions in our bank on this topic. Choose an answer to see why every option is right or wrong.
A year after removal of a skull base tumour, a 60-year-old man's tongue deviates to the right on protrusion, and the right half of the tongue is shrunken and soft with a sharp line at the midline. What has happened to the muscle of the right half of the tongue?
Answer: Fatty replacement of denervated muscle
Injury to the hypoglossal nerve denervates the intrinsic and extrinsic tongue muscles on that side, and the tongue deviates towards the weak side on protrusion because the healthy genioglossus pushes unopposed. In the early phase denervated muscle is oedematous. Over months it atrophies and is replaced by fat, giving a shrunken, soft hemitongue sharply limited by the midline septum. On MRI the fat makes it bright on T1, which should not be mistaken for tumour.
Denervated hemitongue
- Hypoglossal injury
- Tongue deviates to the weak side
- Early oedema, late fatty atrophy
- Sharp midline boundary
Remember Shrunken, soft half-tongue: look along CN XII.
Exam trap Fasciculation of the wasted half points to a lower motor neurone lesion, as with a nerve injury.
Why the other options are wrong
- Acute oedema of denervated muscle Oedema occurs in the first weeks, not a year later, and causes swelling.
- Haemorrhage into the tongue Would cause swelling and bruising, not uniform shrinkage.
- Recurrent tumour in the tongue Would form a firm mass rather than a shrunken hemitongue.
- Venous congestion of the tongue Would cause swelling, not atrophy.
A 30-year-old woman has a firm, painless lump in her right parotid with no enlarged nodes and a normal facial nerve. Which is the preferred way to obtain a tissue diagnosis before surgery?
Answer: Fine-needle aspiration cytology
Most parotid lumps are pleomorphic adenomas, whose thin capsule has small projections of tumour. Cutting into the tumour with an open biopsy spills cells into the wound, causing multiple recurrences, and risks injury to branches of the facial nerve. Fine-needle aspiration, often guided by ultrasound, gives a cytological diagnosis safely with minimal seeding. Definitive treatment is then superficial parotidectomy with preservation of the facial nerve.
Parotid lump diagnosis
- Most are pleomorphic adenomas
- Open biopsy seeds tumour
- Use fine-needle aspiration
- Treat by superficial parotidectomy
Remember Never cut into a parotid lump; aspirate it.
Exam trap Recurrent pleomorphic adenoma after enucleation is often multinodular and hard to cure.
Why the other options are wrong
- Open incisional biopsy Seeds tumour cells and risks the facial nerve.
- Enucleation with frozen section Enucleation leaves capsular projections behind and leads to recurrence.
- Excision of an adjacent node There are no enlarged nodes, and node excision would not diagnose the lump.
- Biopsy through the parotid duct Not a route for sampling a mass within the gland.
A 32-year-old man with untreated HIV infection has soft, painless swelling of both parotid glands. Aspiration shows they are cystic, and he also has enlarged adenoids and many small cervical lymph nodes. What is the most likely diagnosis?
Answer: Benign lymphoepithelial cysts
Benign lymphoepithelial lesions of HIV produce multiple bilateral parotid cysts with solid lymphoid components. They form because the parotid is the only salivary gland that contains intraglandular lymph nodes, and HIV-related lymphoid hyperplasia traps ductal epithelium within them. The triad of bilateral parotid cysts, adenoid hypertrophy and cervical lymphadenopathy is typical. The lesions shrink with antiretroviral therapy.
HIV parotid cysts
- Multiple bilateral parotid cysts
- With adenoid hypertrophy
- And cervical nodes
- Parotid has intraglandular nodes
Remember Bilateral parotid cysts in a young man: think HIV.
Exam trap Bilateral parotid cysts in a young adult should prompt an HIV test.
Why the other options are wrong
- Bilateral Warthin tumours Usually in older male smokers, without adenoid hypertrophy.
- Acute bacterial parotitis Painful, unilateral and febrile.
- Parotid metastases Uncommon and solid, often from skin cancer of the scalp or face.
- Sjogren syndrome Causes dry eyes and mouth with firm gland enlargement rather than cysts with adenoid enlargement.
A 5-year-old snores loudly, breathes through his mouth and has a nasal voice. Enlargement of lymphoid tissue on the posterosuperior wall of the nasopharynx is narrowing his airway. Which structure is enlarged?
Answer: Pharyngeal tonsil
The pharyngeal tonsil (adenoids) is lymphoid tissue in the roof and posterior wall of the nasopharynx. It is largest between about 3 and 7 years and regresses by adolescence. Enlargement narrows the nasopharyngeal airway, causing mouth breathing, snoring and a hyponasal voice, and may block the Eustachian tubes. Long-standing mouth breathing gives the 'adenoid facies'.
Adenoid hypertrophy
- Pharyngeal tonsil on posterosuperior wall
- Largest at 3-7 years
- Mouth breathing, hyponasal voice
- Regresses by adolescence
Remember Mouth-breathing child: check the adenoids.
Exam trap A nasopharyngeal mass in an adult is not adenoids until proven otherwise.
Why the other options are wrong
- Palatine tonsil Lies in the oropharynx between the faucial pillars, below the nasopharynx.
- Lingual tonsil Lies on the tongue base.
- Tubal tonsil Small lymphoid tissue around the Eustachian tube opening, not the posterior wall.
- Thyroid tissue Ectopic thyroid lies at the tongue base, not the nasopharynx.
A tumour in the right hypoglossal canal paralyses the right side of the tongue, but one muscle that helps close the oropharyngeal isthmus still works. Which muscle is spared?
Answer: Palatoglossus
All the intrinsic and extrinsic muscles of the tongue are supplied by the hypoglossal nerve except palatoglossus. Palatoglossus is a palatal muscle supplied by the vagus through the pharyngeal plexus. It forms the palatoglossal arch and raises the back of the tongue while drawing the arches together, closing the oropharyngeal isthmus during swallowing. A hypoglossal lesion therefore spares it.
Palatoglossus
- Only tongue muscle not supplied by XII
- Supplied by vagus (pharyngeal plexus)
- Forms the palatoglossal arch
- Closes the oropharyngeal isthmus
Remember Palatoglossus belongs to the palate and the vagus.
Exam trap Do not count palatoglossus with the hypoglossal muscles just because it is attached to the tongue.
Why the other options are wrong
- Styloglossus Supplied by the hypoglossal nerve.
- Hyoglossus Supplied by the hypoglossal nerve.
- Genioglossus Supplied by the hypoglossal nerve.
- Superior longitudinal An intrinsic muscle supplied by the hypoglossal nerve.
Where this sits in the CPSP syllabus
- Diagnostic Radiology, Paper 2: Head and neck, Oral cavity, salivary glands, pharynx and its spaces, nasopharynx